Agronomic Rates Research Articles

Distinct Responses in Ammonia-Oxidizing Archaea and Bacteria after Addition of Biosolids to an Agricultural Soil

The recently discovered ammonia-oxidizing archaea (AOA) have been suggested as contributors to the first step of nitrification in terrestrial ecosystems, a role that was previously assigned exclusively to ammonia-oxidizing bacteria (AOB). The current study assessed the effects of agricultural management, specifically amendment of soil with biosolids or synthetic fertilizer, on nitrification rates and copy numbers of archaeal and bacterial ammonia monooxygenase (amoA) genes. Anaerobically digested biosolids or synthetic fertilizer was applied annually for three consecutive years to field plots used for corn production. Biosolids were applied at two loading rates, a typical agronomic rate (27 Mg hectare(-1) year(-1)) and double the agronomic rate (54 Mg hectare(-1) year(-1)), while synthetic fertilizer was applied at an agronomic rate typical for the region (291 kg N hectare(-1) year(-1)). Both biosolids amendments and synthetic fertilizer increased soil N and corn yield, but only the biosolids amendments resulted in significant increases in nitrification rates and increases in the copy numbers of archaeal and bacterial amoA genes. In addition, only archaeal amoA gene copy numbers increased in response to biosolids applied at the typical agronomic rate and showed a significant correlation with nitrification rates. Finally, copy numbers of archaeal amoA genes were significantly higher than copy numbers of bacterial amoA genes for all treatments. These results implicate AOA as being primarily responsible for the increased nitrification observed in an agricultural soil amended with biosolids. These results also support the hypothesis that physiological differences between AOA and AOB may enable them to occupy distinct ecological niches.

Microbial and Chemical Markers: Runoff Transfer in Animal Manure-Amended Soils

Fecal contamination of water resources is evaluated by the enumeration of the fecal coliforms and Enterococci. However, the enumeration of these indicators does not allow us to differentiate between the sources of fecal contamination. Therefore, it is important to use alternative indicators of fecal contamination to identify livestock contamination in surface waters. The concentration of fecal indicators (, enteroccoci, and F-specific bacteriophages), microbiological markers (Rum-2-bac, Pig-2-bac, and ), and chemical fingerprints (sterols and stanols and other chemical compounds analyzed by 3D-fluorescence excitation-matrix spectroscopy) were determined in runoff waters generated by an artificial rainfall simulator. Three replicate plot experiments were conducted with swine slurry and cattle manure at agronomic nitrogen application rates. Low amounts of bacterial indicators (1.9-4.7%) are released in runoff water from swine-slurry-amended soils, whereas greater amounts (1.1-28.3%) of these indicators are released in runoff water from cattle-manure-amended soils. Microbial and chemical markers from animal manure were transferred to runoff water, allowing discrimination between swine and cattle fecal contamination in the environment via runoff after manure spreading. Host-specific bacterial and chemical markers were quantified for the first time in runoff waters samples after the experimental spreading of swine slurry or cattle manure.

Agronomic and Economic Benefits of Garden Organics Compost in Vegetable Production

Little research has been carried out on the agronomic and economic value of compost produced from garden organics for vegetable production. A field experiment was established in Camden, near Sydney, Australia (i) to evaluate the effect of the compost on vegetable production (ii) and to evaluate the economic returns from using compost in vegetable production. A total of five vegetable crops were grown and the results indicated that a once only application of compost at an agronomic rate of nitrogen (125 t/ha) produced similar or higher vegetable yields than that of current farmer's practice. For four of the five crops grown, yield was similar, and for one of the crops (capsicum), compost treatment yielded 21% higher than that of the farmers' practice. In addition to soil health benefits, using compost at this rate also resulted in considerable saving of chemical fertilisers. Over the period of the experimental trial, there was a 36% saving in urea as well as 100% saving in P and K fertilisers. For the Mixed treatment (compost at half rate and supplemented by chemical fertilisers), vegetable yield was similar to that of the farmers' practice for the first four crops but this declined to only 64% of that of the farmers' practice for the final crop of leek. Benefit cost analyses showed that for the vegetable compost trial, application of compost provided a benefit cost ratio (BCR) of 1 after five vegetable crops, indicating that this practice was very close to breaking even. On the other hand, BCR of Mix treatment (compost at half rate and supplemented by inorganic fertiliser) was negative due to significant yield decline after growing four crops.

Persistence of triclocarban and triclosan in soils after land application of biosolids and bioaccumulation in Eisenia foetida

The presence of the antimicrobial chemicals triclocarban (TCC) and triclosan (TCS) in municipal biosolids has raised concerns about the potential impacts of these chemicals on soil ecosystems following land application of municipal biosolids. The relative persistence of TCC and TCS in agricultural fields receiving yearly applications of biosolids at six different loading rates over a three-year period was investigated. Soil and biosolids samples were collected, extracted, and analyzed for TCC and TCS using liquid chromatography-tandem mass spectrometry. In addition, the potential for bioaccumulation of TCC and TCS from the biosolids-amended soils was assessed over 28 d in the earthworm Eisenia foetida. Standard 28-d bioaccumulation tests were conducted for three biosolids loading rates from two sites, representing agronomic and twice the agronomic rates of biosolids application plots as well as control plots receiving no applications of biosolids. Additional bioaccumulation kinetic data were collected for the soils receiving the high biosolids loadings to ensure attainment of quasi steady-state conditions. The results indicate that TCC is relatively more persistent in biosolids-amended soil than TCS. In addition, TCC bioaccumulated in E. foetida, reaching body burdens of 25 ± 4 and 133 ± 17 ng/g(ww) in worms exposed for 28 d to the two soils amended with biosolids at agronomic rates. The 28-d organic carbon and lipid-normalized biota soil accumulation factors (BSAFs) were calculated for TCC and ranged from 0.22 ± 0.12 to 0.71 ± 0.13. These findings suggest that TCC bioaccumulation is somewhat consistent with the traditional hydrophobic organic contaminant (HOC) partitioning paradigm. However, these data also suggest substantially reduced bioavailability of TCC in biosolids-amended soils compared with HOC partitioning theory.

Biochar mediated alterations in herbicide breakdown and leaching in soil

Abstract Biochar application to soil has been proposed as a mechanism for improving soil quality and the long term sequestration of carbon. The implications of biochar on pesticide behavior, particularly in the longer term, however, remains poorly understood. Here we evaluated the influence of biochar type, time after incorporation into soil, dose rate and particle size on the sorption, biodegradation and leaching of the herbicide simazine. We show that typical agronomic application rates of biochar (10–100 t ha−1) led to alterations in soil water herbicide concentrations, availability, transport and spatial heterogeneity. Overall, biochar suppressed simazine biodegradation and reduced simazine leaching. These responses were induced by a rapid and strong sorption of simazine to the biochar which limits its availability to microbial communities. Spatial imaging of 14C-labeled simazine revealed concentrated hotpsots of herbicide co-localized with biochar in the soil profile. The rate of simazine mineralization, amount of sorption and leaching was inversely correlated with biochar particle size. Biochar aged in the field for 2 years had the same effect as fresh biochar on the sorption and mineralization of simazine, suggesting that the effects of biochar on herbicide behavior may be long lasting. We conclude that biochar application to soil will reduce the dissipation of foliar applied pesticides decreasing the risk of environmental contamination and human exposure via transfer in the food chain, but may affect the efficacy of soil-applied herbicides.

The Effect of MSW Compost and Fertilizer on Extractable Soil Elements, Tuber Yield, and Elemental Concentrations in the Plant Tissue of Potato

Municipal solid waste (MSW) compost is readily available in eastern Canada and may be a good source of fertility. A 3-year experiment evaluated the effects of MSW compost and fertilizer on soil fertility, elemental composition and yield of potato (Solanum tuberosum L.) grown in a sandy loam soil. Three rates of compost (MSW1, MSW2, and MSW3), one rate of fertilizer (NPK), and one mixture of 1/2 MSW1 compost and 1/2 NPK fertilizer were applied annually to plots in a three-crop rotation; each year the MSW1 rate attempted to match the rate of P applied in the NPK treatment. Mehlich-3 extracts were evaluated for 11 elements at two soil depths (0–15 and 15–30 cm). Potato shoots and roots or whole plants were assessed for 16 elements. Treatments had no consistent significant influence on marketable tuber yields although the NPK treatment produced mathematically the highest yields. After 3 years, treatments had influenced soil concentrations of K, Ca, S, Cu, Zn, and Na in Mehlich-3 extracts at the 0–15 cm depth, but only the concentration of Na at the 15–30 cm depth. The concentration of Mg in the plant tissue was consistently highest in plants fertilized with NPK; this treatment also produced higher Mn concentrations in the last 2 years. Shoot Cu concentrations were highest in the MSW3 plots. The compost did not increase heavy metal concentrations in shoot, root or whole-plant tissue and would be safe to use at agronomic rates of application.

Nitrate pollution of groundwater in Toyserkan, western Iran

A total of 95 groundwater samples were collected from Toyserkan, western Iran to assess the chemical composition and nitrate (NO3 −) status of groundwater. The most prevalent water type is Ca–HCO3 followed by water types Ca–Mg–HCO3. In comparison with the World Health Organization (WHO) drinking water guideline of 50 mg l−1 for NO3 −, a total of nine wells (9.5%) showed higher concentrations. In 36% of samples (34) NO3 − concentration was low ( 47 mg l−1, NO3 − > 27 mg l−1). The high correlation between NO3 − and Cl− (r = 0.86, p < 0.01) is consistent with a manure source, resulting from the practice of adding salt to animal feed. Pollution of groundwaters appeared to be affected by the application of inorganic fertilizer at greater than agronomic rates, Cl-salt inputs, and irrigation practice.

Use of Biosolids to Enhance Rangeland Forage Quality

Biosolids land application was demonstrated to be a potentially cost-effective means for restoring forage productivity and enhancing soil-moisture-holding capacity on disturbed rangelands. By land-applying aerobically digested, anaerobically digested, composted, and lime-stabilized biosolids on rangeland test plots at rates of up to 20 times (20X) the estimated nitrogen-based agronomic rate, forage yields were found to increase from 132.8 kg/ha (118.2 lb/ac) (control plots) to 1182.3 kg/ha (1052.8 lb/ac). Despite the environmental benefits associated with increased forage yield (e.g., reduced soil erosion, improved drainage, and enhanced terrestrial carbon sequestration), the type of forage generated both before and after biosolids land application was found to be dominated by invasive weeds, all of which were characterized as having fair to poor nutritional value. Opportunistic and shallow rooting invasive weeds not only have marginal nutritional value, they also limit the establishment of native perennial grasses and thus biodiversity. Many of the identified invasive species (e.g., Cheatgrass) mature early, a characteristic that significantly increases the fuel loads that support the increased frequency and extent of western wildfires.

Nutrient and aluminum availability of alum-amended poultry litter: a long-term weathering study

To develop agronomic application rates for alum-amended poultry litter, nutrient and Al availability of this particular organic fertilizer were examined using long-term field weathering studies. It was revealed that concentrations of N, P, K+, and Al3+ in the poultry litter leachate ranged from 5 to 6,503 mg L-1, 2 to 84 mg L-1, 2 to 5135 mg L-1, and 0.05 to 4.6 mg L-1, respectively. Release of nutrients occurred principally in the first growing season and would last for years. During 19 months of field weathering, 10.5 kg N, 1.1 kg P, 34.5 kg K+, and 0.031 kg Al3+ were released per ton of the poultry litter and recovered in the leachate. The results suggest that no Al toxicity would be generated to crops if alum-amended poultry litter is used as a fertilizer. If applied at 13.3 ton ha-1, the poultry litter will supply 150.0 kg ha-1 N, 15.2 kg ha-1 P, and 456.2 kg ha-1 K+ to seasonal crops. Application of alum-amended poultry litter at available N-based rates will meet crop nutrient requirements while minimizing nutrient runoff losses.

Metals in biosolids-amended soils in Western Utah

Land application of biosolids has been shown to benefit degraded rangeland; however, soil metal accumulation has been a concern. To date, nine heavy metals found in land applied biosolids are regulated by the United States Environmental Protection Agency. Concern increases when application rates exceed the agronomic rate. The objective of this study was to monitor changes in soil metal accumulation from a one-time biosolids surface application on disturbed rangeland in Western Utah. Two types of biosolids, aerobically digested and lime stabilized, were applied at rates up to twenty times (20x) the estimated agronomic rate. Biosolids were not incorporated into the soil. Levels of heavy metals were recorded at five different soil depths, 0.2, 0.6, 0.9, 1.2 and 1.5 m. The one-time application was evaluated over a two year period. No significant consistent trend between metal concentration, biosolids application rate, biosolids type, year, and soil depth was found. It was concluded that metal concentrations in this study were below the cumulative loading rate from the 40 Code of Federal Regulations (CFR) Part 503 rule. These findings can help alleviate concerns about environmental and health risks due to metal accumulation from biosolids land application.

Nutrient value of alum-treated poultry litter for land application

Alum-treated poultry litter has different chemical composition and biological properties than conventional poultry litter. To develop agronomic application rates for this particular organic fertilizer to cropland, the nutrient value (nutrient plant availability) of alum-treated poultry litter needs to be determined. Typical alum-treated poultry litter was collected from a broiler farm and examined for nutrient content, nutrient release kinetics, and nutrient value by leaching the material for 190 d under simulated weathering conditions. Nutrients recovered in the leachate were characterized and treated as the potentially plant-available portion. The artificial leaching revealed that alum-treated poultry litter released 21.4 g of dissolved organic C, 13.8 g of total dissolved N, 0.6 g of total dissolved P, and 34.6 g of K per kilogram into leachate during the 190-d weathering. The predominant nutrient release occurred in the first 5 wk and fit first-order exponential rise-to-maximum models (for dissolved organic C, total dissolved P, total dissolved N, NH4-N, K+, Na+, Cl−, and SO42−) and logarithmic equations (for Ca2+ and Mg2+). The nutrient value of alum-treated poultry litter is estimated at N, 13.8 g·kg−1; P, 0.75 g·kg−1; K, 34.6 g·kg−1; and S, 24.2 g·kg−1. The concentration of Al in litter leachate remained below 0.2 mM and thus no Al toxicity should be concerned. Based on these results, it is recommended to apply alum-treated poultry litter at 7.3 t·ha−1 for achieving an N supply of 100 kg·ha−1 to common field crops while preventing excessive P runoff losses from high test P soils.

Nutrient dynamics of field-weathered Delmarva poultry litter: implications for land application

To develop phosphorus-based agronomic application rates of phytase-diet, bisulfate-amended Delmarva poultry litter in conservation tillage systems, nutrient release dynamics of the organic fertilizer under local weather conditions were investigated. Delmarva poultry litter was placed in polyvinyl chloride columns to a depth of 5 cm and weathered in the field for 570 days. Leachate from the columns was collected and measured for concentrations of various nutrients. Cumulative release of the nutrients as a function of weathering time was modeled, and the nutrient supply capacity was determined. Poultry litter leachate contained high contents of dissolved organic carbon (15–31,500 mg L−1), nitrogen (N 5–7,070 mg L−1), phosphorus (P 5–230 mg L−1), potassium (K+ 2–7,140 mg L−1), and other nutrients. Release of most nutrients occurred principally in the first 100 days, but for P and calcium (Ca2+), it would last for years. The release kinetics of N followed a logarithm equation, while P and K demonstrated a sigmoidal logistic pattern. The nutrient supply capacity of surface-applied Delmarva poultry litter was predicted at 10.9 kg N Mg−1, 6.5 kg P Mg−1, 34.7 kg K+ Mg−1, 5.4 kg Ca2+ Mg−1, and 14.0 kg SO42− Mg−1. The results suggest that Delmarva poultry litter should be applied to conservation tillage systems at 6.6 Mg ha−1 that would furnish 25 kg P ha−1 and 63 kg N ha−1 to seasonal crops. In repeated annual applications, the rate should be reduced to 5.2 Mg ha−1, with supplemental N fertilization to meet crop N requirements.

Net fluxes of CO 2, but not N 2O or CH 4, are affected following agronomic-scale additions of urea to prairie and arable soils

While experimental addition of nitrogen (N) tends to enhance soil fluxes of carbon dioxide (CO 2), methane (CH 4), and nitrous oxide (N 2O), it is not known if lower and agronomic-scale additions of urea-N applied also enhance trace gas fluxes, particularly for semi-arid agricultural lands in the northern plains. We aimed to test if this were true at agronomic rates [low (11 kg N ha −1), moderate (56 kg N ha −1), and high (112 kg N ha −1)] for central North Dakota arable and prairie soils using intact soil cores to minimize disturbance and simulate field conditions. Additions of urea to cores incubated at 21 °C and 57% water-filled pore space enhanced fluxes of CO 2 but not CH 4 and N 2O. At low, moderate, and high urea-N, CO 2 fluxes were significantly greater than control but not fluxes of CH 4 and N 2O. The increases in CO 2 emission with rate of urea-N application indicate that agronomic-scale N inputs may stimulate microbial carbon cycling in these soils, and that the contribution of CO 2 to net greenhouse gas source strength following fertilization of semi-arid agroecosystems may at times be greater than contributions by N 2O and CH 4.

Three Experimental Systems to Evaluate Phosphorus Supply from Enhanced Granulated Manure Ash

Three experimental systems were used to evaluate a new P fertilizer since residual P levels at typical farm sites may make response detection unlikely. The systems were (i) greenhouse with low P soil, (ii) long‐term research sites with preexisting soil P gradients, and (iii) agricultural fields with prior P fertilization based on agronomic recommendations. The new fertilizer (animal waste by‐product, AWP: 5% N, 28% P2O5, 4% K2O, and 1% S) is an enhanced granulated manure ash. Corn (Zea mays L.), wheat (Triticum aestivum L.), and soybean [Glycine max (L.) Merr.] growth, P uptake, and residual soil Mehlich‐3 P were measured with agronomic rates of AWP or triple superphosphate (TSP). Greenhouse corn and wheat P uptake, and soil Mehlich‐3 P increased similarly with either fertilizer at rates equivalent to 0, 10, 20, 40, and 80 kg P ha−1. In long‐term research sites, grain yield increased with P fertilization in 8 of 12 tests, and was greater with TSP than with AWP in 3 of 12 tests. Plant P uptake increased in all 12 tests, and was greater with TSP in 1 of 12 tests. In previously fertilized agricultural fields, soil Mehlich‐3 P, but not yield, increased due to P fertilization. Fertilizer source differences were infrequent and relatively minor, but possibly due to lower water soluble P content of the AWP (70% versus 78% for TSP). Evaluation of such products requires an appropriate experimental system with low P soils that may be difficult to find on typical North Carolina farms.

Predicting Biosolids Application Rates for Dryland Wheat across a Range of Northwest Climate Zones

We evaluated dryland wheat (Triticum aestivum L.) response to biosolids applications in the inland Pacific Northwest and compared agronomic application rates predicted from yield curves with those predicted from Extension guidance. We applied biosolids rate treatments during the fallow year in 10 on‐farm experiments and determined grain yield, protein, and postharvest soil nitrate. Nitrogen (N) rates were calculated from Extension guidance and compared with biosolids agronomic rate estimates based on yield regressions generated for each site. Eight of the 10 sites had quadratic yield responses. The agronomic biosolids rate at the responsive sites averaged 315 kg ha−1 more grain than the farmer inorganic N rate. At responsive sites, a mean biosolids application rate of 4.7 dry Mg ha−1 (226 kg total N ha−1) was required for 95% of maximum grain yield. Results showed that Extension fertilizer guidance together with calculations for biosolids available N gave reasonable estimates for biosolids application rates.

Inactivation of high concentration of pathogens in land-applied food industry sludge

In Mexico, as in other developing countries, the most important pollution and management problems of food-processing sludge are the high levels of pathogen microorganisms within the sludge and the lack of sites for its disposal. The aims of this study were to evaluate the effect of calcium oxide in the inactivation of pathogenic microorganisms and the subsequent use of the resulting product in an agricultural application at various agronomic rates. Stabilisation tests were done in a hermetically closed fibreglass reactor with 1.5 . capacity, using physicochemical sludge with concentrations of 4, 8 and 12% of total solids (TS) and contact times of 30, 60 and 90 min. At the end of each treatment, the raw and treated sludge quality was evaluated. Recommended doses for Class A biosolids production were 20, 10 and 8% m/m of CaO for 4, 8 and 12% of TS respectively with a minimum contact time of 90 min. The land-application test was done using sludge with 8% TS treated with a quicklime dose of 10% m/m. Nitrogen-based Agronomic Rates (AR) of 0, 1, 5, 10 and 15 were evaluated in the cultivation and production of chayote (Sechium edule). The results with 5 AR showed an estimated total production of 70 kg of the vegetable species over a period of 90 d, which is higher than that reported for the same crop grown without biosolids application.

Land Application of Aluminum Water Treatment Residual: Aluminum Phytoavailability and Forage Yield

Negative impacts of land‐applied aluminum (Al)–rich water treatment residuals (WTRs), which have been suggested to improve soil phosphorus (P) sorption, could include excessive immobilization of plant‐available P and Al phytotoxicity. We studied the impacts of an Al‐rich WTRs on agronomic returns and plant Al concentrations in glasshouse and field studies. The glasshouse study was a 4 × 2 × 3 factorial experiment with one control in a randomized complete block design and three replicates. Four sources of P were each applied at two agronomic rate [44 kg P ha−1, P‐based rate; and 179 kg plant‐available nitrogen (PAN) ha−1, N‐based rate] to topsoil (0–15 cm) of a sandy, siliceous, hyperthermic Arenic Alaquods. Three WTR rates (0, 10, and 25 g kg−1 oven‐dry‐weight basis) were further applied, whereas the control received neither P source nor WTRs. Bahiagrass (Paspalum notatum Fluggae), ryegrass (Lolium perenne L.), and a second bahiagrass crop were continuously grown in succession for 18 months. Applied WTRs increased soil Al but not plant Al concentrations (22–80 mg Al kg−1), which fell within the normal concentration range for pasture plants. In the glasshouse, when WTRs were incorporated with the soil, bahiagrass dry matter (DM) accumulation was reduced, but ryegrass DM was not affected even at 25 g kg−1 WTR. A 2‐year field study, with same treatments but two rates of WTRs (0 and 10 g kg−1 WTR) surface applied to established bahiagrass on the same soil type (Spodosols) showed neither reduced yields nor increased plant Al phytoavailability in the WTR treatments. The studies show no increase in plant Al is associated with Al‐WTRs applied to reduce excess soil‐soluble P and P losses but plant DM accumulation may be reduced.

Simulation of Effects of Swine Manure Application Rates on Nitrate Concentration in Runoff, Indiana, USA

Livestock manure is an important source of nutrients for crop production. However, farmers typically do not know the exact nutrient values for livestock manure. In many instances, manure has been viewed as a waste, and as a result it is applied close to the source resulting in over application of nutrients. Thus, the goal of nutrient application has often been applied to reduce the application expense rather than to maximize crop income. This results in wasted money and potentially negative impacts on water quality. Several livestock manure management scenarios were created based on agronomic nutrient requirements using the Utilization of Animal Manure as a Plant Nutrient (AMANURE) software to investigate water quality impacts with the National Agricultural Pesticide Risk Analysis (NAPRA) WWW modeling system. Application of manure at agronomic rates can result in high nitrate-nitrogen losses for some soil types, especially when applied in late fall. The application of manure at an agronomic rate does not necessarily equate to adequate water quality protection, and farmers must take care applying manure at agronomic rates, because nitrate-nitrogen loss potential varies spatially and temporarily. Nutrient loss probability maps for Indiana at 5%, 10%, 25%, and 50% values were created to demonstrate potential water quality impacts when livestock manure is applied to cropland at agronomic rates. The NAPRA WWW system coupled with AMANURE can be used to identify site-specific livestock manure management plans that are environmentally sound and agronomically appropriate.

Nutrient release from bisulfate-amended phytase-diet poultry litter under simulated weathering conditions

Poultry litter generated on the Delmarva Peninsula is from phytase-modified bird diet and bisulfate amendment. To establish agronomic application rates in conservation tillage systems, bisulfate-amended phytase-diet poultry litter was investigated for its nutrient release kinetics and supply capacity under simulated weathering conditions. Delmarva poultry litter was packed in PVC columns (15 cm i.d. x 25 cm height) to a depth of 5 cm and leached intermittently with 600 mm of water for 190 days. Concentrations of various nutrients in leachate were analyzed and nutrient release kinetics were modelled. Poultry litter leachate contained high contents of dissolved organic carbon (DOC, 35-11,800 mg L(-1)), nitrogen (N 6-2690 mg L(-1)), phosphorus (P 45-225 mg L(-1)), potassium (K 20-6060 mg L(-1)), and other nutrients. Release of the nutrients occurred primarily in the starting 5 weeks and mostly followed a first order Exponential-Rise-to-Maximum model. Under the specified conditions, the poultry litter demonstrated a nutrient supply capacity of 11.7 kg N Mg(-1), 5.4 kg P Mg(-1), and 36.8 kg K Mg(-1). Release of the potentially plant-available N and K was nearly finalized within 190 days of leaching/weathering, but it would require two years for full release of the leachable P. The results indicate that with consideration of field conditions, surface application of bisulfate-amended phytase-diet Delmarva poultry litter at recommended 6.6 Mg ha(-1) to conservation tillage systems would largely provide P 25.0 kg ha(-1), N 106.6 kg ha(-1), and K 245.5 kg ha(-1) to seasonal crops.

Fate of 4-nonylphenol in a biosolids amended soil

The fate of the endocrine disrupting compound 4-nonylphenol (NP) in an agricultural soil amended with biosolids was assessed in a greenhouse study. A biosolids with a total NP concentration of 900 mg kg −1 was incorporated into the 4 cm surface layer of soil columns at an agronomic rate equivalent to 1.7 kg m 2. Half of the columns were planted with Triticum aestivum L., red hardy winter wheat seeds, whereas the remaining columns were unplanted to evaluate the influence of plant growth on the fate of NP. The degradation of total NP and eight NP isomers was monitored over 45 d. The half-life of NP in this soil system ranged from 16 to 23 d depending on treatment. After 45 d from the start of the trail, 15% of the initial biosolids-NP remained in the planted columns, whereas ∼30% remained in the unplanted columns, indicating enhanced degradation in the presence of plants. The eight NP isomers exhibited different degradation rates, but minimal amounts of all isomers persisted after 45 d. Movement of NP below the zone of incorporation was slight (<2% of total NP present at any sampling interval) and no NP was detected in column leachates or in wheat leaves.